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  <div class="section" id="module-pty">
<span id="pty-pseudo-terminal-utilities"></span><h1>35.8. <a class="reference internal" href="#module-pty" title="pty: Pseudo-Terminal Handling for Linux. (Linux)"><code class="xref py py-mod docutils literal"><span class="pre">pty</span></code></a> — Pseudo-terminal utilities<a class="headerlink" href="#module-pty" title="Permalink to this headline">¶</a></h1>
<p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.6/Lib/pty.py">Lib/pty.py</a></p>
<hr class="docutils" />
<p>The <a class="reference internal" href="#module-pty" title="pty: Pseudo-Terminal Handling for Linux. (Linux)"><code class="xref py py-mod docutils literal"><span class="pre">pty</span></code></a> module defines operations for handling the pseudo-terminal
concept: starting another process and being able to write to and read from its
controlling terminal programmatically.</p>
<p>Because pseudo-terminal handling is highly platform dependent, there is code to
do it only for Linux. (The Linux code is supposed to work on other platforms,
but hasn’t been tested yet.)</p>
<p>The <a class="reference internal" href="#module-pty" title="pty: Pseudo-Terminal Handling for Linux. (Linux)"><code class="xref py py-mod docutils literal"><span class="pre">pty</span></code></a> module defines the following functions:</p>
<dl class="function">
<dt id="pty.fork">
<code class="descclassname">pty.</code><code class="descname">fork</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#pty.fork" title="Permalink to this definition">¶</a></dt>
<dd><p>Fork. Connect the child’s controlling terminal to a pseudo-terminal. Return
value is <code class="docutils literal"><span class="pre">(pid,</span> <span class="pre">fd)</span></code>. Note that the child  gets <em>pid</em> 0, and the <em>fd</em> is
<em>invalid</em>. The parent’s return value is the <em>pid</em> of the child, and <em>fd</em> is a
file descriptor connected to the child’s controlling terminal (and also to the
child’s standard input and output).</p>
</dd></dl>

<dl class="function">
<dt id="pty.openpty">
<code class="descclassname">pty.</code><code class="descname">openpty</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#pty.openpty" title="Permalink to this definition">¶</a></dt>
<dd><p>Open a new pseudo-terminal pair, using <a class="reference internal" href="os.html#os.openpty" title="os.openpty"><code class="xref py py-func docutils literal"><span class="pre">os.openpty()</span></code></a> if possible, or
emulation code for generic Unix systems. Return a pair of file descriptors
<code class="docutils literal"><span class="pre">(master,</span> <span class="pre">slave)</span></code>, for the master and the slave end, respectively.</p>
</dd></dl>

<dl class="function">
<dt id="pty.spawn">
<code class="descclassname">pty.</code><code class="descname">spawn</code><span class="sig-paren">(</span><em>argv</em><span class="optional">[</span>, <em>master_read</em><span class="optional">[</span>, <em>stdin_read</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#pty.spawn" title="Permalink to this definition">¶</a></dt>
<dd><p>Spawn a process, and connect its controlling terminal with the current
process’s standard io. This is often used to baffle programs which insist on
reading from the controlling terminal.</p>
<p>The functions <em>master_read</em> and <em>stdin_read</em> should be functions which read from
a file descriptor. The defaults try to read 1024 bytes each time they are
called.</p>
<div class="versionchanged">
<p><span class="versionmodified">Changed in version 3.4: </span><a class="reference internal" href="#pty.spawn" title="pty.spawn"><code class="xref py py-func docutils literal"><span class="pre">spawn()</span></code></a> now returns the status value from <a class="reference internal" href="os.html#os.waitpid" title="os.waitpid"><code class="xref py py-func docutils literal"><span class="pre">os.waitpid()</span></code></a>
on the child process.</p>
</div>
</dd></dl>

<div class="section" id="example">
<h2>35.8.1. Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h2>
<p>The following program acts like the Unix command <em class="manpage">script(1)</em>, using a
pseudo-terminal to record all input and output of a terminal session in a
“typescript”.</p>
<div class="highlight-python3"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">argparse</span>
<span class="kn">import</span> <span class="nn">os</span>
<span class="kn">import</span> <span class="nn">pty</span>
<span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">import</span> <span class="nn">time</span>

<span class="n">parser</span> <span class="o">=</span> <span class="n">argparse</span><span class="o">.</span><span class="n">ArgumentParser</span><span class="p">()</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">&#39;-a&#39;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">&#39;append&#39;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s1">&#39;store_true&#39;</span><span class="p">)</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">&#39;-p&#39;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">&#39;use_python&#39;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s1">&#39;store_true&#39;</span><span class="p">)</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">&#39;filename&#39;</span><span class="p">,</span> <span class="n">nargs</span><span class="o">=</span><span class="s1">&#39;?&#39;</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="s1">&#39;typescript&#39;</span><span class="p">)</span>
<span class="n">options</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">()</span>

<span class="n">shell</span> <span class="o">=</span> <span class="n">sys</span><span class="o">.</span><span class="n">executable</span> <span class="k">if</span> <span class="n">options</span><span class="o">.</span><span class="n">use_python</span> <span class="k">else</span> <span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s1">&#39;SHELL&#39;</span><span class="p">,</span> <span class="s1">&#39;sh&#39;</span><span class="p">)</span>
<span class="n">filename</span> <span class="o">=</span> <span class="n">options</span><span class="o">.</span><span class="n">filename</span>
<span class="n">mode</span> <span class="o">=</span> <span class="s1">&#39;ab&#39;</span> <span class="k">if</span> <span class="n">options</span><span class="o">.</span><span class="n">append</span> <span class="k">else</span> <span class="s1">&#39;wb&#39;</span>

<span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="n">filename</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span> <span class="k">as</span> <span class="n">script</span><span class="p">:</span>
    <span class="k">def</span> <span class="nf">read</span><span class="p">(</span><span class="n">fd</span><span class="p">):</span>
        <span class="n">data</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="mi">1024</span><span class="p">)</span>
        <span class="n">script</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
        <span class="k">return</span> <span class="n">data</span>

    <span class="nb">print</span><span class="p">(</span><span class="s1">&#39;Script started, file is&#39;</span><span class="p">,</span> <span class="n">filename</span><span class="p">)</span>
    <span class="n">script</span><span class="o">.</span><span class="n">write</span><span class="p">((</span><span class="s1">&#39;Script started on </span><span class="si">%s</span><span class="se">\n</span><span class="s1">&#39;</span> <span class="o">%</span> <span class="n">time</span><span class="o">.</span><span class="n">asctime</span><span class="p">())</span><span class="o">.</span><span class="n">encode</span><span class="p">())</span>

    <span class="n">pty</span><span class="o">.</span><span class="n">spawn</span><span class="p">(</span><span class="n">shell</span><span class="p">,</span> <span class="n">read</span><span class="p">)</span>

    <span class="n">script</span><span class="o">.</span><span class="n">write</span><span class="p">((</span><span class="s1">&#39;Script done on </span><span class="si">%s</span><span class="se">\n</span><span class="s1">&#39;</span> <span class="o">%</span> <span class="n">time</span><span class="o">.</span><span class="n">asctime</span><span class="p">())</span><span class="o">.</span><span class="n">encode</span><span class="p">())</span>
    <span class="nb">print</span><span class="p">(</span><span class="s1">&#39;Script done, file is&#39;</span><span class="p">,</span> <span class="n">filename</span><span class="p">)</span>
</pre></div>
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  <ul>
<li><a class="reference internal" href="#">35.8. <code class="docutils literal"><span class="pre">pty</span></code> — Pseudo-terminal utilities</a><ul>
<li><a class="reference internal" href="#example">35.8.1. Example</a></li>
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  <h4>Previous topic</h4>
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